Simmons was the lead military official involved in the May 2003 expulsion of 14 Cuban spies serving under diplomatic cover, the third largest explosion of diplomats in U.S. history. As a result of Simmons and other agents actions, Alberto Coll, a professor and former deputy assistant secretary of defense was arrested.

Simmons served in Grenada, the Balkans, Iraq and Afghanistan and interrogated more than 732 terrorists and other “high-value individuals” throughout his career. He was part of the special operations unit “Task Force 6-26” and spent a total of 28 years in government service.